Peptide therapies for ocular surface disturbances based on fibronectin-integrin interactions

Mechanism of Endogenous Peptide PDYBX1 and Precursor Protein YBX1 in Hirschsprung's Disease

Endogenous peptides, bioactive agents with a small molecular weight and outstanding absorbability, regulate various cellular processes and diseases. However, their role in the occurrence of Hirschsprung's disease (HSCR) remains unclear. Here, we found that the expression of an endogenous peptide derived from YBX1 (termed PDYBX1 in this study) was upregulated in the aganglionic colonic tissue of HSCR patients, whereas its precursor protein YBX1 was downregulated. As shown by Transwell and cytoskeleton staining assays, silencing YBX1 inhibited the migration of enteric neural cells, and this effect was partially reversed after treatment with PDYBX1. Moreover, immunoprecipitation and immunofluorescence revealed that ERK2 bound to YBX1 and PDYBX1. Downregulation of YBX1 blocked the ERK1/2 pathway, but upregulation of PDYBX1 counteracted this effect by binding to ERK2, thereby promoting cell migration and proliferation. Taken together, the endogenous peptide PDYBX1 may partially alleviate the inhibition of the ERK1/2 pathway caused by the downregulation of its precursor protein YBX1 to antagonize the impairment of enteric neural cells. PDYBX1 may be exploited to design a novel potential therapeutic agent for HSCR.

The Role of Insulin-like Growth Factor (IGF) System in the Corneal Epithelium Homeostasis-From Limbal Epithelial Stem Cells to Therapeutic Applications

The corneal epithelium, comprising three layers of cells, represents the outermost portion of the eye and functions as a vital protective barrier while concurrently serving as a critical refractive structure. Maintaining its homeostasis involves a complex regenerative process facilitated by the functions of the lacrimal gland, tear film, and corneal nerves. Crucially, limbal epithelial stem cells located in the limbus (transitional zone between the cornea and the conjunctiva) are instrumental for the corneal epithelium integrity by replenishing and renewing cells. Re-epithelialization failure results in persistent defects, often associated with various ocular conditions including diabetic keratopathy. The insulin-like growth factor (IGF) system is a sophisticated network of insulin and other proteins essential for numerous physiological processes. This review examines its role in maintaining the corneal epithelium homeostasis, with a special focus on the interplay with corneal limbal stem cells and the potential therapeutic applications of the system components.

Tenascins and osteopontin in biological response in cornea

The structural composition, integrity and regular curvature of the cornea contribute to the maintenance of its transparency and vision. Disruption of its integrity caused by injury results in scarring, inflammation and neovascularization followed by losses in transparency. These sight compromising effects is caused by dysfunctional corneal resident cell responses induced by the wound healing process. Upregulation of growth factors/cytokines and neuropeptides affect development of aberrant behavior. These factors trigger keratocytes to first transform into activated fibroblasts and then to myofibroblasts. Myofibroblasts express extracellular matrix components for tissue repair and contract the tissue to facilitate wound closure. Proper remodeling following primary repair is critical for restoration of transparency and visual function. Extracellular matrix components contributing to the healing process are divided into two groups; a group of classical tissue structural components and matrix macromolecules that modulate cell behaviors/activities besides being integrated into the matrix structure. The latter components are designated as matricellular proteins. Their functionality is elicited through mechanisms which modulate the scaffold integrity, cell behaviors, activation/inactivation of either growth factors or cytoplasmic signaling regulation. We discuss here the functional roles of matricellular proteins in mediating injury-induced corneal tissue repair. The roles are described of major matricellular proteins, which include tenascin C, tenascin X and osteopontin. Focus is directed towards dealing with their roles in modulating individual activities of wound healing-related growth factors, e. g., transforming growth factor β (TGF β). Modulation of matricellular protein functions could encompass a potential novel strategy to improve the outcome of injury-induced corneal wound healing.

Highly stable fibronectin-mimetic-peptide-based supramolecular hydrogel to accelerate corneal wound healing

Without timely treatment, poor wound healing in corneal injuries can seriously impair vision and lead to blindness. Thus, it is vital to develop a therapeutic strategy to accelerate corneal re-epithelialization. The conjugation of self-assembled motifs with a fibronectin-mimetic peptide sequence (PHSRN) drastically improves the chemical stability of PHSRN against protease hydrolysis and minimally affects its biological activity to promote the migration of corneal epithelial cells. The optimized Nap-FFPHSRN self-assembled into bioactive supramolecular hydrogels increases cell motility by remolding F-actin and boosts the tight junction of the corneal epithelium by increasing the expression of zonula occludens-1 (ZO-1). An in vivo experiment showed that a Nap-FFPHSRN hydrogel provided extended precorneal retention with good ocular tolerance after topical instillation. An animal model of corneal scrape showed that a single daily dose of Nap-FFPHSRN hydrogel had a superior therapeutic effect in facilitating corneal re-epithelialization with complete morphological and architectural recovery. With a rational approach to mimic bioactive proteins, this study presents a new strategy to demonstrate the potential of peptide-based supramolecular hydrogels for use in clinical treatment of corneal injury. STATEMENT OF SIGNIFICANCE: Here we systematically investigate the self-assembly behavior and chemical stability of designed peptide amphiphiles (Nap-FPHRSN, Nap-FFPHSRN and Nap-FFFPHSRN). The introduction of self-assembled motifs (Nap-F, Nap-FF and Nap-FFF) drastically enhances the chemical stability of fibronectin-mimetic peptide (PHSRN). Moreover, topical instillation of Nap-FFPHSRN hydrogel once daily, exhibits a better in vivo effect than PHSRN and the same in vivo effect as fibronectin, both of which are instilled three times daily, for promoting full morphological and architectural recovery after corneal re-epithelialization. As a rational design of conjugating bioactive peptides with self-assembled motifs to mimic bioactive proteins, this work may lead to a new approach that improves the in vivo therapeutic effect for treating corneal injury in clinic settings.

Corneal neurotization in the management of neurotrophic keratopathy: A review of the literature

Neurotrophic keratopathy (NK) is a rare degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia or anesthesia. Neurotrophic corneal ulcers are notoriously difficult to treat and can lead to blindness. Corneal neurotization (CN) is a recent surgical technique aimed at restoring corneal sensation and may offer a definitive treatment in the wake of NK. Herein, we review the surgical techniques utilized in direct and indirect CN. Technical considerations, outcomes, current limitations and future perspectives are also discussed. This article highlights the key points of this promising procedure and biological aspects that will help provide the best treatment options for patients with severe NK.

Changes in TRPV1 Expression as Well as Substance P and Vasoactive Intestinal Peptide Levels Are Associated with Recurrence of Pterygium

Pterygium, a disease of the ocular surface, is characterized by the proliferation and invasion of fibrovascular tissue. Chronic inflammation contributes to pterygium occurrence. Sensory neuropeptides of TRPV1-positive nerve fibers are involved in inflammation and corneal wound healing. The possible association between TRPV1 in nerve fibers and neuropeptides such as Substance P (SP) and Vasoactive Intestinal Peptide (VIP) in the recurrence of pterygium has not been examined before. The pterygia from 64 patients were used to determine changes in SP and VIP levels using 10 min acetic-acid extraction that yielded mainly neuronal peptides. There was a sufficient amount of pterygium tissues from the 35 patients for further immunohistochemical analysis of TRPV1 and S100, which is a glial marker to visualize nerve fibers. SP and VIP levels increased markedly in cases with primary and secondary recurrences, and there was a close correlation between SP and VIP levels. TRPV1 expression increased in the epithelium, while stromal expression decreased in recurrences. Nerve fibers were demonstrated mainly in the stroma, and serial sections confirmed the localization of TRPV1 with the nerve fibers. These results together with previous findings demonstrated that the increased epithelial expression of TRPV1 in recurrent pterygia might be involved in the pathogenesis, and the inhibition of epithelial TRPV1 activity may prevent recurrence.

Expression Pattern of Tenascin-C, Matrilin-2, and Aggrecan in Diseases Affecting the Corneal Endothelium

Purpose: The aim of this study was to examine the expression pattern of tenascin-C, matrilin-2, and aggrecan in irreversible corneal endothelial pathology such as pseudophakic bullous keratopathy (PBK) and Fuchs’ endothelial corneal dystrophy (FECD), which most frequently require corneal transplantation. Materials and methods: Histological specimens of corneal buttons removed during keratoplasty were investigated in PBK (n = 20) and FECD (n = 9) and compared to healthy control corneas (n = 10). The sections were studied by chromogenic immunohistochemistry (CHR-IHC) and submitted for evaluation by two investigators. Semiquantitative scoring (0 to 3+) was applied according to standardized methods at high magnification (400x). Each layer of the cornea was investigated; in addition, the stroma was subdivided into anterior, middle, and posterior parts for more precise analysis. In case of non-parametric distribution Mann−Whitney test was applied to compare two groups. Kruskal−Wallis and Dunn’s multiple comparisons tests have been applied for comparison of the chromogenic IHC signal intensity among corneal layers within the control and patient groups. Differences of p < 0.05 were considered as significant. Results: Significantly elevated tenascin-C immunopositivity was present in the epithelium and every layer of the stroma in both pathologic conditions as compared to normal controls. In addition, also significantly stronger matrilin-2 positivity was detected in the epithelium; however, weaker reaction was present in the endothelium in PBK cases. Minimal, but significantly elevated immunopositivity could be observed in the anterior and posterior stroma in the FECD group. Additionally, minimally, but significantly higher aggrecan immunoreaction was present in the anterior stroma in PBK and in the posterior stroma in both endothelial disorders. All three antibodies disclosed the strongest reaction in the posterior stroma either in PBK or in FECD cases. Conclusions: These extracellular matrix molecules disclosed up to moderate immunopositivity in the corneal layers in varying extents. Through their networking, bridging, and adhesive abilities these proteins are involved in corneal regeneration and tissue reorganization in endothelial dysfunction.

Protein and polypeptide mediated delivery to the eye

Hybrid or recombinant protein-polymers, peptide-based biomaterials, and antibody-targeted therapeutics are widely explored for various ocular conditions and vision correction. They have been noted for their potential biocompatibility, potency, adaptability, and opportunities for sustained drug delivery. Unique to peptide and protein therapeutics, their production by cellular translation allows their precise modification through genetic engineering. To a greater extent than drug delivery to other systems, delivery to the eye can benefit from the combination of locally-targeted administration and protein-based specificity. Consequently, a range of delivery platforms and administration methods have been exploited to address the ocular delivery of peptide and protein biomaterials. This review discusses a sample of preclinical and clinical opportunities for peptide-based drug delivery to the eye.

Drug-peptide supramolecular hydrogel boosting transcorneal permeability and pharmacological activity via ligand-receptor interaction

Boosting transcorneal permeability and pharmacological activity of drug poses a great challenge in the field of ocular drug delivery. In the present study, we propose a drug-peptide supramolecular hydrogel based on anti-inflammatory drug, dexamethasone (Dex), and Arg-Gly-Asp (RGD) motif for boosting transcorneal permeability and pharmacological activity via the ligand-receptor interaction. The drug-peptide (Dex-SA-RGD/RGE) supramolecular hydrogel comprised of uniform nanotube architecture formed spontaneously in phosphate buffered saline (PBS, pH = 7.4) without external stimuli. Upon storage at 4 °C, 25 °C, and 37 °C for 70 days, Dex-SA-RGD in hydrogel did not undergo significant hydrolysis, suggesting great long-term stability. In comparison to Dex-SA-RGE, Dex-SA-RGD exhibited a more potent in vitro anti-inflammatory efficacy in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages via the inhibition of nuclear factor кB (NF-κB) signal pathway. More importantly, using drug-peptide supramolecular hydrogel labeled with 7-nitro-2,1,3-benzoxadiazole (NBD), the Dex-SA-K(NBD)RGD showed increased performance in terms of integrin targeting and cellular uptake compared to Dex-SA-K(NBD)RGE, as revealed by cellular uptake assay. On topical instillation in rabbit's eye, the proposed Dex-SA-K(NBD)RGD could effectively enhance the transcorneal distribution and permeability with respect to the Dex-SA-K(NBD)RGE. Overall, our findings demonstrate the performance of the ligand-receptor interaction for boosting transcorneal permeability and pharmacological activity of drug.

Characterization of plasmatic proteins adsorption on poly(styrene sodium sulfonate) functionalized silicone surfaces

Proteins adsorption occurs spontaneously on biomaterial upon insertion within the body. The resulting protein layer influences biomaterial biocompatibility through enhanced bio-integration or, on the contrary, adverse reactions. Furthermore, upon adsorption, proteins can undergo modifications of their structure and, ultimately, their physicochemical properties and activity. Hence, the understanding of protein adsorption on implanted materials appears essential, as exemplified by silicone breast prostheses that might lead to serious health issues. Surface modifications with a bioactive polymer, poly(styrene sodium sulfonate)-polyNaSS, on a hydrophobic silicone surface that composes breast implants, have been successfully performed under UV irradiation by a radical surface polymerization. This strategy enhances cell biocompatibility and antibacterial features. Although detailed insights related to the mechanism are still scarce, polyNaSS is supposed to promote changes in the conformation and/or orientation of adsorbed plasma proteins, reducing the odd for a biofilm to form. The present work addresses more in-depth structural investigations of the adsorbed state of two plasma proteins: Bovine Serum Albumin (BSA), as a model protein, and fibronectin (FN), for its role in cell adhesion. Using Atomic force microscopy (AFM), we report that polyNaSS showed no significant impact on the BSA structure conversely to the FN one. However, imaging findings with AFM clearly outlined a change in the structural organization of FN, going from a nano fibrillar assembly with an average length of 130 nm to a globular one when the surface was grafted. Thus, it is highlighted that polyNaSS interacts specifically with FN. In addition, cell spreading assay of L929 fibroblasts on FN-coated surfaces with optical microscopy indicated no significant impact of the change in FN structure upon fibroblasts adhesion, which displayed active elongated shapes. The present features are crucial for understanding the cell adhesion mechanism induced by surface modification.

Immunity and pain in the eye: focus on the ocular surface

Most ocular diseases are associated with pain. While pain has been generally considered a mere (deleterious) additional symptom, it is now emerging that it is a key modulator of innate/adaptive immunity. Because the cornea receives the highest nerve density of the entire body, it is an ideal site to demonstrate interactions between pain and the immune response. Indeed, most neuropeptides involved in pain generation are also potent regulators of innate and adaptive leukocyte physiology. On the other hand, most inflammatory cells can modulate the generation of ocular pain through release of specific mediators (cytokines, chemokines, growth factors, and lipid mediators). This review will discuss the reciprocal role(s) of ocular surface (and specifically: corneal) pain on the immune response of the eye. Finally, we will discuss the clinical implications of such reciprocal interactions in the context of highly prevalent corneal diseases.

Effects of Amniotic Membrane Extract Eye Drops on Persistent Epithelial Defects of the Cornea

Purpose: To evaluate the clinical efficacy of amniotic membrane extract eye drops (AMEEDs) in patients with persistent epithelial defects (PEDs) of the cornea.Methods: Sixteen patients with PEDs refractory to the conventional treatment were further treated with AMEEDs six times a day. Visual acuity, visual analog scale (VAS), esthesiometer score, and areas of the epithelial defects before and after 1 and 2 months of treatment were evaluated. After 2 months, AMEEDs were considered effective if all epithelial defects were healed, partially effective if the epithelial defects decreased in size compared with the baseline, and ineffective if the epithelial defects increased in size and required additional treatment.Results: After 2 months of treatment with AMEEDs, there was a reduction in the area of epithelial defects (5.2 ± 3.1 mm2 vs. 0.1 ± 0.1 mm2, respectively, p = 0.01), as well as a significant improvement in best-corrected visual acuity (0.8 ± 0.5 logarithm of minimal angle of resolution [LogMAR] vs. 0.6 ± 0.3 LogMAR, respectively, p = 0.03), and VAS scores (4.3 ± 1.0 vs. 2.8 ± 0.7, respectively, p = 0.04) compared with the baseline values. Treatment with AMEEDs was effective in 13 (81.3%) patients and partially effective in three (18.8%) patients.Conclusions: AMEEDs could stimulate epithelial wound healing and improve ocular symptoms in patients with refractory PED. Therefore, AMEEDs could be considered an effective treatment option for refractory PEDs.

Gelatin hydrogel/contact lens composites as rutin delivery systems for promoting corneal wound healing

Corneal wound healing is a highly regulated biological process that is of importance for reducing the risk of blinding corneal infections and inflammations. Traditional eye drop was the main approach for promoting corneal wound healing. However, its low bioavailability required a high therapeutic concentration, which can lead to ocular or even systemic side effects. To develop a safe and effective method for treating corneal injury, we fabricated rutin-encapsulated gelatin hydrogel/contact lens composites by dual crosslinking reactions including in situ free radical polymerization and carboxymethyl cellulose/N-hydroxysulfosuccinimide crosslinking. In vitro drug release results evidenced that rutin in the composites could be sustainedly released for up to 14 days. In addition, biocompatibility assay indicated nontoxicity of the composites. Finally, the effect of rutin-encapsulated composites on the healing of the corneal injury in rabbits was investigated. The injury was basically cured in corneas using rutin-encapsulated composites (healing rate, 98.3% ± 0.7%) at 48 h post-operation, while the damage was still present in corneas using the composite (healing rate, 87.0% ± 4.5%). Further proteomics analysis revealed that corneal wound healing may be promoted by the ERK/MAPK and PI3K/AKT signal pathways. These results inform a potential intervention strategy to facilitate corneal wound healing in humans.

USP10 Promotes Fibronectin Recycling, Secretion, and Organization

Purpose

Integrins play a central role in myofibroblast pathological adhesion, over-contraction, and TGFβ activation. Previously, we demonstrated that after corneal wounding, αv integrins are protected from intracellular degradation by upregulation of the deubiquitinase USP10, leading to cell-surface integrin accumulation. Because integrins bind to and internalize extracellular matrix (ECM), we tested whether extracellular fibronectin (FN) accumulation can result from an increase in integrin and matrix recycling in primary human corneal fibroblasts (HCFs).

Methods

Primary HCFs were isolated from cadaver eyes. HCFs were transfected with either USP10 cDNA or control cDNA by nucleofection. Internalized FN was quantified with a FN ELISA. Recycled extracellular integrin and FN were detected with streptavidin-488 by live cell confocal microscopy (Zeiss LSM 780). Endogenous FN extra domain A was detected by immunocytochemistry. Cell size and removal of FN from the cell surface was determined by flow cytometry.

Results

USP10 overexpression increased α5β1 (1.9-fold; P < 0.001) and αv (1.7-fold; P < 0.05) integrin recycling, with a concomitant increase in biotinylated FN internalization (2.1-fold; P < 0.05) and recycling over 4 days (1.7–2.2-fold; P < 0.05). The dependence of FN recycling on integrins was demonstrated by α5β1 and αv integrin blocking antibodies, which, compared with control IgG, decreased biotinylated FN recycling (62% and 84%, respectively; P < 0.05). Overall, we established that extracellular FN was composed of approximately 1/3 recycled biotinylated FN and 2/3 endogenously secreted FN.

Conclusions

Our data suggest that reduced integrin degradation with a subsequent increase in integrin/FN recycling after wounding may be a newly identified mechanism for the characteristic accumulation of ECM in corneal scar tissue.

Nuclear translocation of β-catenin induced by E-cadherin endocytosis causes recurrent erosion of diabetic cornea

Recurrent epithelial erosion and refractory corneal ulcer are the clinical features of diabetic keratopathy (DK), which eventually lead to corneal scar and visual disturbance. In this study, we sought to determine the abnormalities of cell junction in diabetic corneal epithelial cells and the effect of high glucose on the β-catenin/E-cadherin complex. Corneal histology showed that corneal epithelial cells of high glucose mice were loosely arranged, and the immunohistochemistry showed that the expression of E-cadherin decreased, the levels of β-catenin increased in nuclear. High glucose-induced degradation and endocytosis of E-cadherin of corneal epithelial cells reduce the formation of β-catenin/E-cadherin complex and promote the nuclear translocation of β-catenin. Moreover, high glucose also activated the transcription and expression of matrix metallopeptidase and snail, which interfered with the adhesion of corneal epithelial cells to the basement membrane. These findings reveal that DK is associated with the dissociation of cell junctions. The maintenance of the stability of the β-catenin/E-cadherin complex may be a potential therapeutic target of refractory corneal ulcers in patients with diabetes.

The fibrinolytic system in the cornea: A key regulator of corneal wound healing and biological defense

The cornea is a relatively unique tissue in the body in that it possesses specific features such as a lack of blood vessels that contribute to its transparency. The cornea is supplied with soluble blood components such as albumin, globulin, and fibrinogen as well as with nutrients, oxygen, and bioactive substances by diffusion from aqueous humor and limbal vessels as well as a result of its exposure to tear fluid. The healthy cornea is largely devoid of cellular components of blood such as polymorphonuclear leukocytes, monocytes-macrophages, and platelets. The location of the cornea at the ocular surface renders it susceptible to external insults, and its avascular nature necessitates the operation of healing and defense mechanisms in a manner independent of a direct blood supply. The fibrinolytic system, which was first recognized for its role in the degradation of fibrin clots in the vasculature, has also been found to contribute to various biological processes outside of blood vessels. Fibrinolytic factors thus play an important role in biological defense of the cornea. In this review, we address the function of the fibrinolytic system in corneal defense including wound healing and the inflammatory response.

Role of the Neurokinin-1 Receptor in the Promotion of Corneal Epithelial Wound Healing by the Peptides FGLM-NH2 and SSSR in Neurotrophic Keratopathy

Purpose

Neurotrophic keratopathy is a corneal epitheliopathy induced by trigeminal denervation that can be treated with eyedrops containing the neuropeptide substance P (or the peptide FGLM-NH₂ derived therefrom) and insulin-like growth factor 1 (or the peptide SSSR derived therefrom). Here, we examine the mechanism by which substance P (or FGLM-NH₂) promotes corneal epithelial wound healing in a mouse model of neurotrophic keratopathy.

Methods

The left eye of mice subjected to trigeminal nerve axotomy in the right eye served as a model of neurotrophic keratopathy. Corneal epithelial wound healing was monitored by fluorescein staining and slit-lamp examination. The distribution of substance P, neurokinin-1 receptor (NK-1R), and phosphorylated Akt was examined by immunohistofluorescence analysis. Cytokine and chemokine concentrations in intraocular fluid were measured with a multiplex assay.

Results

Topical administration of FGLM-NH₂ and SSSR promoted corneal epithelial wound healing in the neurotrophic keratopathy model in a manner sensitive to the NK-1R antagonist L-733,060. Expression of substance P and NK-1R in the superficial layer of the corneal epithelium decreased and increased, respectively, in model mice compared with healthy mice. FGLM-NH₂ and SSSR treatment suppressed the production of interleukin-1α, macrophage inflammatory protein 1α (MIP-1α) and MIP-1β induced by corneal epithelial injury in the model mice. It also increased the amount of phosphorylated Akt in the corneal epithelium during wound healing in a manner sensitive to prior L-733,060 administration.

Conclusions

The substance P–NK-1R axis promotes corneal epithelial wound healing in a neurotrophic keratopathy model in association with upregulation of Akt signaling and attenuation of changes in the cytokine-chemokine network.

Activation of Nell-1 in BMSC Sheet Promotes Implant Osseointegration Through Regulating Runx2/Osterix Axis

Neural epidermal growth factor-like 1 protein (Nell-1) is first studied because of its association with human craniosynostosis. Nell-1 has been used to accelerate the process of fracture healing because of the osteoinductive ability in recent years. However, the role of Nell-1 during the process of osteointegration is unknown. Here we show that activation of Nell-1 in the BMSC sheet promotes osseointegration in vivo and in vitro. We found that overexpression of Nell-1 improved osteogenic differentiation and enhanced matrix mineralization of BMSCs through increasing expression of Runx2 and Osterix. Activation of Nell-1 up-regulated the expression ratio of OPG/RANKL, which might have a negative influence on osteoclast differentiation. Furthermore, we obtained BMSC sheet-implant complexes transfected with lentivirus overexpressing and interfering Nell-1 in in vivo study, and confirmed that overexpression of Nell-1 promoted new bone formation around the implant and increased the bone-implant contacting area percentage. Our results demonstrate that activation of Nell-1 improves implant osteointegration by regulating Runx2/Osterix axis and shows the potential of BMSC sheet-implant complexes in gene therapy.

Effect of epidermal growth factor ointment on persistent epithelial defects of the cornea

Background

Healthy corneal epithelium acts as a barrier against damage to the deeper structures in the eye. Failure in the mechanisms of corneal epithelization can lead to persistent epithelial defects of the cornea (PEDs) and can compromise its function. Epidermal growth factor (EGF) promotes the proliferation, migration, and differentiation of epithelial cells, endothelial cells, and fibroblasts during wound healing and may be beneficial in treating patients with PEDs. We, therefore, investigated the effect of EGF ointment on patients with PEDs.

Methods

Fifteen patients with PEDs refractory to conventional treatment were treated twice a day with EGF ointment. Patient demographics and comorbidities were noted. The epithelial healing time was determined along with the primary outcome measures in the areas of the epithelial defects, visual acuity, visual analog scale (VAS) scores, and esthesiometer scores 1 month and 2 months after treatment.

Results

Five eyes of herpetic keratitis (33.3%), 3 eyes of dry eye disease (20.0%), 3 eyes of bacterial keratitis (20.0%), 2 eyes of limbal stem cell deficiency (13.3%), 1 eye of diabetic neurotrophic keratitis (6.7%), and 1 eye of filamentary keratitis (6.7%) were associated with PEDs, respectively. Two months following treatment with EGF ointment, there was a reduction in the area of the epithelial defects (5.7 ± 3.9 to 0.1 ± 0.3 mm²) as well as a significant improvement in best-corrected visual acuity (0.9 ± 0.8 to 0.6 ± 0.5 LogMAR) and VAS scores (4.5 ± 1.2 to 2.5 ± 0.7) in 12 eyes (80%). Among these cases, the mean epithelial healing time was 5.5 ± 1.8 weeks. Amniotic membrane transplantation was performed on the remaining 3 (20.0%) patients that did not respond to EGF treatment.

Conclusions

EGF ointment could reduce symptoms and promotes corneal epithelialization of refractory PEDs. It may, therefore, be well-tolerated and a potentially beneficial addition in the management of refractory PEDs.

Peptidomic analysis of zebrafish embryos exposed to polychlorinated biphenyls and their impact on eye development

Polychlorinated biphenyls (PCBs), a class of persistent organic pollutant, are closely related to abnormal eye development in children. However, little is known regarding the role of peptides in the development of PCB-induced ocular dysplasia. To characterize the nature of PCB exposure on peptides involved in the development of the ocular system, we used liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) to detect differential expression of peptides between normal and PCB-exposed zebrafish embryos. A total of 7900 peptides were analyzed, 90 of which were differentially expressed, with 29 being up-regulated and 61 down-regulated. These peptides were investigated using ingenuity pathway analysis (IPA) and gene ontology (GO) analysis to explore their role in eye development. This study identified 18 peptides associated with the development of the optic nerve and ocular system in the PCB-exposure group, as well as 10 peptides that are located in the functional domain of their precursor proteins. These peptides provide potential biomarkers for the treatment of ocular dysplasia caused by PCBs and may help us understand the mechanism of abnormal eye development caused by organic pollutants.

Tetrahedral Framework Nucleic Acids Promote Corneal Epithelial Wound Healing in Vitro and in Vivo

Poor post-traumatic wound healing can affect the normal function of damaged tissues and organs. For example, poor healing of corneal epithelial injuries may lead to permanent visual impairment. It is of great importance to find a therapeutic way to promote wound closure. Tetrahedral framework nucleic acids (tFNAs) are new promising nanomaterials, which can affect the biological behavior of cells. In the experiment, corneal wound healing is used as an example to explore the effect of tFNAs on wound healing. Results show that the proliferation and migration of human corneal epithelial cells are enhanced by exposure to tFNAs in vitro, possibly relevant to the activation of P38 and ERK1/2 signaling pathway. An animal model of corneal alkali burn is established to further identify the facilitation effect of tFNAs on corneal wound healing in vivo. Clinical evaluations and histological analyses show that tFNAs can improve the corneal transparency and accelerate the re-epithelialization of wounds. Both in vitro and in vivo experiments show that tFNAs can play a positive role in corneal epithelial wound healing.

Expansion and maintenance of primary corneal epithelial stem/progenitor cells by inhibition of TGFβ receptor I-mediated signaling

Transforming growth factor β (TGFβ) signaling is one of the most important signaling pathways regulating cell behavior in ocular tissues. Its functions are mainly linked to tissue fibrosis and inflammatory responses in ophthalmology. In epithelial cells, however, the growth inhibitory activity of TGFβ was reported in both non-ocular and ocular tissues. Since TGFβ is a bifunctional regulator that either inhibits or stimulates cell proliferation according to the specific context, we examined the effect of inhibition of TGFβ receptor (TβR) I-mediated signaling on primary corneal epithelial cells (CECs) in serum- and feeder-free conditions. The mouse CECs were isolated from the eyeballs of 6-8 weeks old female C57BL/6 mice using dispase and trypsin separately, cultivated in defined Keratinocyte serum-free medium (KSFM) with supplements (the complete medium) without feeder layer. Cells were divided into three groups, those cultured in complete medium additionally supplemented with 10 μM SB-431542, a specific inhibitor of TβR-I, were SB-CECs; those cultured in complete medium additionally supplemented with 10 ng/ml SRI-011381, a TGF-beta signaling agonist, were SRI-CECs; those cultured in complete medium without SB-431542 or SRI-011381 were control CECs. The growth rate and morphology were analyzed by light microscopy. The identity and stemness of cells was investigated through marker staining of p63, inhibitor of differentiation 1 (ID1), cytokeratin 12 (K12), cytokeratin 14 (K14), PAX6, pSmad3, alpha smooth muscle Actin (αSMA) and E-cadherin (E-cad); Real-time quantitative (RT-PCR) analysis of p63; Western blot analysis of ID1; as well as colony forming assay, sphere forming assay, healing wound in vitro assay and air-lifting interface assay. The results showed SB-CECs subcultured steadily, achieved sustained expansion, and expanded almost thrice faster than control CECs. Expanded SB-CECs exhibited smaller and more compact morphology, up-regulated p63 and ID1, as well as better performed colony-forming capacity, sphere-forming capacity, in vitro wound healing capacity, and the capacity to stratify and differentiate on air-lifting interface. Preliminary tests on human limbal epithelial cells (HLECs) showed the same results as mouse CECs. Interestingly, the ID1 expression pattern was almost identical to p63, the typical marker for corneal epithelial stem/progenitor cell (CESC/CEPC), in cultured CECs and normal corneal sections. Since ID1 has been proven to be regulated negatively by TGFβ signaling in epithelial cells and plays a role in blocking cell differentiation, its derepression by TβR-I inhibitor could be, at least in part, the underlying cause of CESC/CEPC expansion and the synchronously up-regulated expression of p63 in SB-CECs. In conclusion, inhibition of TβR-I-mediated signaling, CESCs/CEPCs achieved efficient long-term expansion in a feeder- and serum-free condition in vitro. And derepression of ID1 could be the underlying cause. Meanwhile, ID1 could serve as a marker for CESC/CEPC. These results may advance the basic and clinical CESC/CEPC research.

Triptolide inhibits TGF-β-induced matrix contraction and fibronectin production mediated by human Tenon fibroblasts

AIM

To determine if triptolide influences the contractility and fibronectin production in human Tenon fibroblasts (HTFs).

METHODS

HTFs were cultured in type I collagen gels with or without transforming growth factor beta (TGF-β) and/or triptolide. The diameter of the collagen gel was used to measure contraction. Immunoblot analysis was used to quantify myosin light chain (MLC) phosphorylation and integrin expression. Laser confocal fluorescence microscopy was used to monitor the formation of actin stress fibers. Fibronectin production was measured with an enzyme immunoassay.

RESULTS

Triptolide inhibition of contraction in TGF-β-induced collagen gel mediated by HTFs was dose-dependent and statistically significant at 3 nmol/L (P<0.05) and maximal at 30 nmol/L and significantly time dependent at 2d (P<0.05). Triptolide reduced TGF-β-induced expression of integrins α5 and β1, phosphorylation of MLC, and formation of stress fibers in HTFs. Furthermore, the inhibition of triptolide on the attenuated TGF-β-induced production of fibronectin by HTFs was concentration-dependent and significant at 1 nmol/L (P<0.05) and maximal at 30 nmol/L.

CONCLUSION

Triptolide suppress the contractility of HTFs induced by TGF-β and the production of fibronectin by these cells. It is promising that triptolide treatment may possibly inhibit scar formation after glaucoma filtration surgery.

Remodeling of the Corneal Epithelial Scaffold for Treatment of Persistent Epithelial Defects in Diabetic Keratopathy

<b><i>Background:</i></b> To develop a strategy based on surgical removal of a degenerated corneal epithelial scaffold for treatment of persistent epithelial defects (PEDs) in diabetic keratopathy. <b><i>Case Presentation:</i></b> Three diabetic patients with PEDs were initially treated with eyedrops containing the fibronectin-based peptide PHSRN (Pro-His-Ser-Arg-Asn) or both the substance P-derived peptide FGLM-NH₂ and the insulin-like growth factor-1-derived peptide SSSR. A degenerated Bowman’s layer or calcified lesion thought to be responsible for incomplete healing was surgically removed after confirmation of reactivity to the peptide eyedrops. All three patients achieved complete epithelial wound closure after surgery. Two cases treated by phototherapeutic keratectomy or lamellar keratoplasty did not show PED recurrence during 6 or 36 months of follow-up, respectively. One case treated by mechanical removal of a degenerated Bowman’s layer manifested recurrence after 1 month, but resurfacing of the defect was again achieved after repeat surgery. <b><i>Conclusion:</i></b> We propose a new strategy for treatment of diabetic PEDs based on surgical remodeling of the corneal epithelial scaffold for patients who respond to peptide eyedrops but fail to achieve wound closure.

Neurotrophic Keratopathy after Trigeminal Nerve Block for Treatment of Postherpetic Neuralgia

Purpose

To report a case of persistent corneal epithelial defect that had occurred after a trigeminal nerve block.

Case Presentation

A 75-year-old female had suffered from postherpetic neuralgia for 8 years. She underwent Gasserian ganglion block surgery and noticed declining visual acuity in the right eye on the following day. She presented with severe hyperemia and corneal epithelial defects in the right eye and experienced remarkable reduction of sensitivity in the right cornea. She was diagnosed with neurotrophic keratopathy. Ofloxacin eye ointment and rebamipide ophthalmic suspension ameliorated the corneal epithelial defects but superficial punctate keratopathy, corneal superficial neovascularization, and Descemet's fold persisted. Although the epithelial defects occasionally recurred, the corneal sensation and epithelial defects, Descemet's fold, and corneal superficial neovascularization all improved around 5 months after trigeminal nerve block. The HRT II Rostock Cornea Module (RCM) could not detect any corneal subbasal nerve fibers at postoperative 4 months; however, it could detect them at postoperative 6 months.

Conclusions

As the nerve block effect wore off, the corneal subbasal nerve fibers slowly regenerated. As the corneal sensation improved, the corneal epithelial defects and superficial neovascularization also improved. The HRT II RCM appeared useful for observing loss and regeneration of the corneal subbasal nerve fibers.

The Effect of Topical Substance-P Plus Insulin-like Growth Factor-1 (IGF-1) on Epithelial Healing After Photorefractive Keratectomy in Rabbits

Purpose

To determine whether topical Substance-P (SP) plus insulin-like growth factor-1 (IGF-1) can improve corneal healing after photorefractive surface ablation in a rabbit.

Methods

After a 9.0-mm corneal de-epithelialization using a combination of chemical (18% alcohol) and mechanical debridement, excimer photorefractive surface ablation was performed bilaterally in eight rabbits (16 eyes) with an 8.0-mm ablation zone and 70-μm depth. The right eye was treated with SP (250 μg/mL) and IGF-1 (25 ng/mL) in hyaluronic acid, one drop twice a day, and the other eye treated with only hyaluronic acid. The epithelial healing process was documented photographically twice a day until healing was complete. Six rabbits were sacrificed 6 weeks after photorefractive keratectomy (PRK) and corneas examined histologically.

Results

Seven of eight rabbit eyes treated with SP/IGF-1 healed in a shorter time than the untreated eye. For rabbit #6, both eyes healed at the same time. The average healing time (total time until wound closure) for the treated eyes was 99 hours, while the average healing time for the untreated eyes was 170 hours (P = 0.0490). A persistent epithelial defect was found in two of the nontreated eyes but none in the treated eyes. Corneal pathology showed some degree of epithelial separation in the central corneal wound in three out of six nontreated eyes and in just the treated eye of rabbit #6.

Conclusion

Topical SP plus IGF-1 increases the epithelial healing rate after PRK. There may have been beneficial effects upon cell adhesion as well.

Translational Relevance

Better and faster healing.

Nanomicelle-Assisted Targeted Ocular Delivery with Enhanced Antiinflammatory Efficacy In Vivo

Ocular inflammations are common diseases that may lead to serious vision-threatening obstacles. Eye drops for antiinflammation therapy need to be administered multiple times daily at a high dosage due to the rapid precorneal removal and low bioavailability of drugs. To overcome these problems, a cRGD-functionalized DSPE-PEG2000 nanomicelle (DSPE-PEG2000-cRGD) encapsulated with flurbiprofen is proposed. The tailored nanomicelles trigger specific binding to integrin receptors on the ocular surface, which leads to rapid and robust mucoadhesion, superior ocular surface retention, and transcorneal penetration behaviors of nanomicelles. Due to the enhanced drug delivery on ocular surface and in aqueous humor, the functionalized nanoformulation significantly improves ocular antiinflammation efficacy at a low dosage by blocking the synthesis of inflammatory mediators and cytokines. The present study demonstrates a promising strategy that uses a functional peptide combined with nanomicelles for targeted delivery to the eye in ophthalmologic applications.

Anti-inflammatory effect of Heliotropium indicum Linn on lipopolysaccharide-induced uveitis in New Zealand white rabbits

AIM

To investigate the anti-inflammatory effect of an aqueous whole plant extract of Heliotropium indicum (HIE) on endotoxin-induced uveitis in New Zealand white rabbits.

METHODS

Clinical signs of uveitis including flares, iris hyperemia and miosis, were sought for and scored in 1.0 mg/kg lipopolysaccharide (LPS) -induced uveitic rabbits treated orally with HIE (30-300 mg/kg), prednisolone (30 mg/kg), or normal saline (10 mL/kg). The number of polymorphonuclear neutrophils infiltrating, the protein concentration, as well as levels of tumor necrosis factor-α (TNF-α), prostaglandin E2 (PGE2), and monocyte chemmoattrant protein-1 (MCP-1) in the aqueous humor after the various treatments were also determined. A histopathological study of the anterior uveal was performed.

RESULTS

The extract and prednisolone-treatment significantly reduced (P≤0.001) both the clinical scores of inflammation (1.0-1.8 compared to 4.40±0.40 in the normal saline-treated rabbits) and inflammatory cells infiltration. The level of protein, and the concentrations of TNF-α, PGE2 and MCP-1 in the aqueous humor were also significantly reduced (P≤0.001). Histopathological studies showed normal uveal morphology in the HIE and prednisolone-treated rabbits while normal saline-treated rabbits showed marked infiltration of inflammatory cells.

CONCLUSION

The HIE exhibits anti-inflammatory effect on LPS-induced uveitis possibly by reducing the production of pro-inflammatory mediators.

Mining for genes related to choroidal neovascularization based on the shortest path algorithm and protein interaction information

BACKGROUND

Choroidal neovascularization (CNV) is a serious eye disease that may cause visual loss, especially for older people. Many factors have been proven to induce this disease including age, gender, obesity, and so on. However, until now, we have had limited knowledge on CNV's pathogenic mechanism. Discovering the genes that underlie this disease and performing extensive studies on them can help us to understand how CNV occurs and design effective treatments.

METHODS

In this study, we designed a computational method to identify novel CNV-related genes in a large protein network constructed using the protein-protein interaction information in STRING. The candidate genes were first extracted from the shortest paths connecting any two known CNV-related genes and then filtered by a permutation test and using knowledge of their linkages to known CNV-related genes.

RESULTS

A list of putative CNV-related candidate genes was accessed by our method. These genes are deemed to have strong relationships with CNV.

CONCLUSIONS

Extensive analyses of several of the putative genes such as ANK1, ITGA4, CD44 and others indicate that they are related to specific biological processes involved in CNV, implying they may be novel CNV-related genes.

GENERAL SIGNIFICANCE

The newfound putative CNV-related genes may provide new insights into CNV and help design more effective treatments. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.